Field of the Invention
This invention generally relates to a coating having heparin attached thereto on an implantable device, such as a stent.
Description of the Background
Blood has a property of being coagulated by the action of various components in blood when it has come into contact with foreign matters. Hence, there is need for a high anticoagulant property in component materials for medical articles or instruments used on the part coming into contact with blood, as exemplified by artificial hearts, artificial cardiac valves, artificial blood vessel, blood vessel catheters cannulas, pump-oxygenators, blood vessel by-pass tubes, intraaortic balloon pumping, transfusion instruments and extracorporeal circulation circuits. Heparin has been commonly used to impart to the medical devices anticoagulant properties, but a systemic use of heparin may undesirably lead to the formation of a large number of bleeding nests.
Methods have been developed to minimize side effects associated with the use of heparin with limited success (see, for example, U.S. Pat. Nos. 5,270,064 and 6,630,580). The efficacy of using heparin not only depends on the nature and property of heparin, but also depends on the nature and property of the materials used in associated with heparin. For example, surfaces in-vivo are quickly covered by proteins, which may thus reduce the effectiveness of heparin attached thereto. Moreover, direct attachment of heparin to substrate surfaces may block the binding sites on the heparin molecule such that they become inaccessible to the binding proteins, further reducing the effectiveness of heparin.
The present invention addresses such problems by providing a coating composition for coating implantable devices.